The IPCC report relies upon six long-term surface temperature datasets to come up with the 0.2°C per decade rate of increase. Interestingly, the report does not cite the two global temperature datasets derived from satellites: the University of Alabama in Huntsville reports that global average temperatures are rising at a rate of 0.13°C per decade, and Remote Sensing Systems reports the rate of increase at 0.18°C per decade. At the UAH rate of warming, the 1.5°C threshold would not be exceeded until around 2070. (Note in passing, recent research suggests that without anthropogenic warming, the planet would already be headed well down the path toward a new ice age.
Concretely, the global GDP of $80 trillion, growing at 3 percent annually, would rise to $903 trillion by 2100. A 2.6 percent reduction means that it would only be $880 trillion by 2100. A 0.3 percent decrease implies a loss of $2.7 trillion resulting in a global GDP of $900 trillion. Note that the IPCC is recommending that the world spend between now and 2035 more than $45 trillion in order to endow $2.7 trillion more in annual income on people living three generations hence. Assuming the worst case loss of 2.6 percent of GDP in world with a population of 10 billion that would mean that they would have to scrape by on an average income of just $88,000 per year (the average global GDP per capita now is $10,500.)https://reason.com/2018/10/11/how-big-o ... degree-of/
A potential small loss of $23 trillion in global GDP if we don't spend at least $45 trillion raping the world of it's rare earth metals. That's the catastrophe liars like May and idiots like AOC say we only have a decade or so to avoid.